1996 Fiscal Year Final Research Report Summary
The analysis of the mechanism of osmoregulation in the inner ear.
| Project/Area Number |
07671879
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Otorhinolaryngology
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| Research Institution | Nara Medical University |
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Principal Investigator |
MATSUNAGA Takashi Nara Medical University, Professor, 医学部, 教授 (10028475)
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| Co-Investigator(Kenkyū-buntansha) |
YAMANAKA Toshiaki Nara Medical University, Teaching assistant, 医学部, 助手 (90271204)
KANATA Hirokazu Nara Medical University, Teaching assistant, 医学部, 助手 (40275326)
UEDA Takashi Nara Medical University, Teaching assistant, 医学部, 助手 (10232753)
YANE Katsuari Nara Medical University, Senior lecturer, 医学部, 講師 (40220199)
FUITA Nobuya Nara Medical University, Senior lecturer, 医学部, 講師 (20165385)
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| Project Period (FY) |
1995 – 1996
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| Keywords | myo-inositol / transporter / SMIT / rat / inner ear / in situ hybridization / hypernatremia / osmoregulation / osmolyte |
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| Research Abstract |
We investigated the expression of sodium myo-inositol cotransporter (SMIT) mRNA in the inner ear and brain of rats by in situ hybridization method to understand the mechanism of the osmoreguration system mediated by osmolytes.
In the cochlea, the most intense SMIT mRNA signals were observed in fibrocytes of the spiral ligament, moderate signals were found in the spiral limbus, inner hair cells and spiral ganglion cells, while the hybridization signals were almost undetectable in the marginal cells of the stria vascularis and outer hair cells. In the vestibular system, moderate hybridization signals were found in the sensory epithelium, fibrocytes and vestibular ganglion cells. These findings suggest that SMIT plays an important role in maintenance of intracellular ionic balance and cell volume in the inner ear, especially in the fibrocytes associated with generation of the ion gradients between the endolymph and perilymph.
And we also investigated the changes in expressions of SMIT mRNA in the brain of acute hypernatremic rats by in situ hybridization and Northern blot methods. Under moderate acute hypernatremic conditions, SMIT mRNA level increased markedly at 1h and returned to almost control levels at 3h, in accordance with plasma Na^+ concentrations. Especially, distinct increase in SMIT mRNA expression were observed in the granule cells and glial cells in the cerebellum. The definite increases of SMIT mRNA expression was not seen in the chronic hypernatremic rats. These findings indicate that SMIT plays an important role in osmoregulation, especially in the early stages of acute hypernatremia in the brain.
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